Applying a sound effect for an effect on a diagram node

[Uzi]

Hi All,

Cycle diagram containing 3 nodes has an 'Appear' animation effect.
Each diagram node is animated separately - there are 3 effects (the
build level is msoAnimateDiagramClockwise)
Programmatically, I set a sound effect for one of the diagram effects.
I do this by using the ImportFile method of SoundEffect property

Here is the code I use to add the sound effect:
PowerPoint.Slide slide = (PowerPoint.Slide)
this.applicationObj.ActiveWindow.View.Slide;
slide.TimeLine.MainSequence[1].EffectInformation.SoundEffect.ImportFromFile(@"c:\temp.wav");

The problem is that after I do this power point changes the sound
effect property to "no sound".
It is possible to do this (set a sound effect to a specific node)
through power point manually and the problem happens only when it's
done programmatically.
also, the problem only occurs

Thanks!

Uzi